1. Field of the Invention
This invention relates to a tape cassette having a tape member stored in a housing. More particularly, it relates to a tape cassette having a covering member for protecting a tape member exposed outside the housing and a lock member for preventing the covering member from moving at the time the cassette is not in use.
2. Related Background Art
A conventional tape cassette, such as a VHS video cassette, is provided with a cover lock member for locking the front cover so that the front cover protecting the tape exposed outside of the housing is prevented from moving when the cassette is not in use. For example, Japanese utility model publication No. 60-20210 discloses a cover lock member which is integrally connected with a spring member formed in a curved board shape wherein the cover lock member is biased by the spring member toward the locking position (See FIG. 6 of the publication). However, if the spring member formed in a curved board shape is kept in a unlocked condition (the tape cassette is inserted into a record reproduction device) for a long period of time and thus the spring member is kept biased during that period, the shape of the spring member may be permanently changed. As a result, the locking force generated by deformation of the board shaped spring member is decreased and the sufficient locking force cannot be maintained.
U.S. Pat. No. 4,466,583 discloses a lock member whose structure is basically the same as the lock member disclosed by the Japanese utility model publication No. 60-20210 although projecting direction of the spring member is different (FIGS. 2 to 5). In this case also, it is difficult to maintain the locking force of the lock member for a long period of time. FIGS. 6 to 9 of the above U.S. Patent further discloses a lock member which utilizes the deformation of a plastic member for generating biasing force. Durability of this lock member is superior to the lock member having the above structure. However, if outside force is applied to the locking projection by impact or the like in such direction that the front cover be opened at a time the cassette is not in use, the deformed portion may be easily ruptured by the force transmitted from the projection owing to the proximate position of the deformed portion to the lock projection. If the deformed portion is ruptured, it can no longer function as a lock member.
The lock member disclosed by Japanese patent Publication No. 2675103 utilizes deformation of a deformable portion. The lock member is excellent in durability having a simple structure. However, since the lock member is fixed to the housing by fitting thereto, workability at assembling may be deteriorated (when the fitting is tight) or the locking force may become insufficient (when the fitting is loose) depending on variations of products. As a result, it is difficult to stably maintain the quality of the products.